Noninvasive Stimulation Of Neurotypic Cells With Photoconductivity

A material’s persistent photoconductivity has, for the first time, been used to stimulate neurotype cells. The relatively simple technique could lead to future research on using charge to influence cellular behavior.

A material that demonstrates persistent photoconductivity gains a negative charge on its surface when exposed to the right wavelength of light, and retains that charge even after the light is removed. The correct wavelength of light, and how long the material retains its charge, varies from material to material.

Researchers have known for years that electric charge can stimulate a cell, but existing technologies for conducting related experiments are often invasive or require specialized equipment. They can also be extremely time consuming.

“We wanted to take advantage of the electronic properties of the semiconductor gallium nitride, which is biocompatible, making it a true bioelectronic interface. The result is a faster, noninvasive way to stimulate cells that doesn’t require specialized equipment.”

Gallium Nitride Substrate

The researchers exposed a gallium nitride substrate to ultraviolet (UV) light, creating a negative charge on its surface.

As soon as the UV light was removed, researchers poured a solution containing PC12 neurotypic cells into the container with the substrate. The researchers then introduced a dye that allowed them to measure calcium levels in the PC12 cells.

PC12 is a cell line derived from a pheochromocytoma of the rat adrenal medulla, that have an embryonic origin from the neural crest that has a mixture of neuroblastic cells and eosinophilic cells.

What the researchers found was that PC12 cells were stimulated when they came into contact with the charged gallium nitride substrate, as evidenced by increased calcium ion levels within the cells, when compared to a control group that did not come into contact with a charged substrate.

This is evidence of altered behavior because ions are important in neurotypic cell activity. For example, calcium ions play key roles in neuronal signaling.

“In addition to advancing our fundamental understanding of what this material is capable of, we’re optimistic that it can facilitate work by many labs interested in advancing research on cellular behavior,”

said Albena Ivanisevic, a professor of materials science and engineering at NC State and corresponding author of the paper.